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Ultrafast broadband circular dichroism in the deep ultraviolet

Oppermann, Malte
Bauer, Benjamin
Rossi, Thomas
Helbing, Jan
Chergui, Majed
Published in Optica. 2019, vol. 6, no. 1, p. 56-60
Abstract The measurement of chirality and its temporal evolution are crucial for the understanding of a large range of biological functions and chemical reactions. Steady-state circular dichroism (CD) is a standard analytical tool for measuring chirality in chemistry and biology. Nevertheless, its push into the ultrafast time domain and in the deep-ultraviolet has remained a challenge, with only some isolated reports of subnanosecond CD. Here, we present a broadband time-resolved CD spectrometer in the deep ultraviolet (UV) spectral range with femtosecond time resolution. The setup employs a photoelastic modulator to achieve shot-to-shot polarization switching of a 20 kHz pulse train of broadband femtosecond deep-UV pulses (250–370 nm). The resulting sequence of alternating left- and right-circularly polarized probe pulses is employed in a pump-probe scheme with shot-to-shot dispersive detection and thus allows for the acquisition of broadband CD spectra of ground- and excited-state species. Through polarization scrambling of the probe pulses prior to detection, artifact-free static and transient CD spectra of enantiopure [Ru(bpy)3]2+ are successfully recorded with a sensitivity of <2×10−5 OD (≈0.7  mdeg). Due to its broadband deep-UV detection with unprecedented sensitivity, the measurement of ultrafast chirality changes in biological systems with amino-acid residues and peptides and of DNA oligomers is now feasible.
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Research group Groupe Lacour
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OPPERMANN, Malte et al. Ultrafast broadband circular dichroism in the deep ultraviolet. In: Optica, 2019, vol. 6, n° 1, p. 56-60. doi: 10.1364/OPTICA.6.000056 https://archive-ouverte.unige.ch/unige:112702

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Deposited on : 2019-01-09

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